There are a number of spinal surgeries in which a fixation or stabilization construct is implanted in a patient and attached to the patient's spine. For example, a typical posterior fixation construct may include one or more longitudinal spinal rods attached to multiple of the patient's vertebrae by respective bone anchors. Exemplary bone anchors can include pedicle or lateral mass screws, hooks, wires, and so forth. The implanted construct extends along a segment of the spine between an uppermost instrumented vertebra (UIV), i.e., the most-superior or most-cranial vertebra to which the construct is attached, and a lowermost instrumented vertebra (LIV), i.e., the most-inferior or most-caudal vertebra to which the construct is attached.
One complication that can arise with these surgeries is an undesired degree of kyphosis at or above the UIV. Proximal junctional kyphosis (PJK) is typically defined as a proximal junctional sagittal Cobb angle greater than 10 degrees, or at least 10 degrees greater than in a pre-operative measurement. It is estimated that between 5% and 46% of adult spine patients suffer from some form of PJK, with most cases being diagnosed weeks or months after the surgery. In some cases, proximal junctional failure (PJF) can occur. PJF may be characterized by (i) post-operative fracture of the UIV or the vertebra superiorly-adjacent thereto (UIV+1), (ii) UIV implant failure, (iii) PJK increase greater than 15 degrees, and/or (iv) a need for proximal extension of the fusion or the construct within 6 months of the surgery. FIG. 1 is a sagittal view of a patient spine S in which PJK/PJF has occurred above the UIV after surgery to implant a fixation construct C. Patients who suffer from PJK or PJF may experience increased pain, neurologic deficit, or ambulatory difficulties, and may be faced with revision surgery and the expenses and risks associated therewith.